Cancer is a leading cause of death worldwide and accounted for approximately 7.6 million deaths (around 13% of all deaths) in 2008 (Ferlay J, et al., GLOBOCAN 2008 v1.2, Cancer Incidence and Mortality Worldwide: IARC CancerBase No. 10 [Internet]. Lyon, France: International Agency for Research on Cancer; 2010). Although significant progress in the treatment of certain types of cancer such as childhood leukemia has been achieved over the past several decades, many of the most common types of cancer remain difficult to manage and are often incurable, particularly if discovered after the tumor has invaded locally or metastasized. Tumors can exhibit marked variability in terms of aggressiveness and response to treatment, despite displaying similar histopathologic features and stage. Such variability can complicate development of appropriate treatment plans for individual patients. There is a need in the art for identification and elucidation of pathways and cellular changes that contribute to malignancy. There is also a need in the art for innovative approaches for tumor prognosis and for selecting appropriate treatment regimens for individuals with cancer.